Lambda Aquarii
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 52m 36.87404s |
| Declination | −07° 34′ 46.5489″ |
| Apparent magnitude (V) | 3.722 (3.57 to 3.80) |
| Characteristics | |
| Evolutionary stage | AGB |
| Spectral type | M2.5 IIIa Fe–1 |
| U−B color index | +1.721 |
| B−V color index | +1.641 |
| Variable type | Lb |
| Astrometry | |
| Radial velocity (Rv) | −10.46±0.53 km/s |
| Proper motion (μ) | RA: +14.964 mas/yr Dec.: +32.742 mas/yr |
| Parallax (π) | 8.9360±0.2356 mas |
| Distance | 365 ± 10 ly (112 ± 3 pc) |
| Absolute magnitude (MV) | −1.5 |
| Details | |
| Mass | 2.96±0.5 M☉ |
| Radius | 100.17+2.67 −2.81 R☉ |
| Luminosity | 1,716 L☉ |
| Temperature | 3,702 K |
| Metallicity [Fe/H] | −2.25 dex |
| Other designations | |
| λ Aqr, 73 Aquarii, BD−08°968, FK5 864, HD 216386, HIP 112961, HR 8698, SAO 146362 | |
| Database references | |
| SIMBAD | data |
Lambda Aquarii, informally known as Hydor (/ˈhaɪdɔːr/), is a variable star in the equatorial constellation of Aquarius. The name is Latinized from the Bayer designation λ Aquarii, and abbreviated Lambda Aqr or λ Aqr. The apparent visual magnitude of this star ranges from 3.57 down to 3.80, which is bright enough to be visible with the naked eye. The star is eclipsed by the sun from about 1-4 March; thus the star can be viewed the whole night, crossing the sky, in early September, in the current epoch. Lambda Aquarii is located at a distance of 365 light-years (112 pc) from the Sun based on parallax, but is drifting closer with a radial velocity of −10.5 km/s.
This star lies just 0.39 degrees south of the ecliptic and so is subject to lunar and planetary occultations. On 16 April 2014, it was occulted by Venus as viewed from Australia, New Zealand and the West Pacific.